8,695 research outputs found
Ab-initio Gorkov-Green's function calculations of open-shell nuclei
We present results from a new ab-initio method that uses the self-consistent
Gorkov Green's function theory to address truly open-shell systems. The
formalism has been recently worked out up to second order and is implemented
here in nuclei for the first time on the basis of realistic nuclear forces. We
find good convergence of the results with respect to the basis size in Ca44 and
Ni74 and discuss quantities of experimental interest including ground-state
energies, pairing gaps and particle addition/removal spectroscopy. These
results demonstrate that the Gorkov method is a valid alternative to
multireference approaches for tackling degenerate or near degenerate quantum
systems. In particular, it increases the number of mid-mass nuclei accessible
in an ab-initio fashion from a few tens to a few hundreds.Comment: 5 pages, 3 figure
Ab-initio self-consistent Gorkov-Green's function calculations of semi-magic nuclei - II. Numerical implementation at second order with a two-nucleon interaction
The newly developed Gorkov-Green's function approach represents a promising
path to the ab initio description of medium-mass open-shell nuclei. We discuss
the implementation of the method at second order with a two-body interaction,
with particular attention to the numerical solution of Gorkov's equation.
Different sources of theoretical error and degrees of self-consistency are
investigated. We show that Krylov projection techniques with a multi-pivot
Lanczos algorithm efficiently handle the growth of poles in the one-body
Green's function when Gorkov's equation is solved self-consistently. The end
result is a tractable, accurate and gently scaling ab initio scheme applicable
to full isotopic chains in the medium-mass region.Comment: 17 pages, 13 figure
Doubly magic nuclei from Lattice QCD forces at 469 MeV/c
We perform ab initio self-consistent Green's function calculations of the
closed shell nuclei He, O and Ca, based on
two-nucleon potentials derived from Lattice QCD simulations, in the flavor
SU(3) limit and at the pseudo-scalar meson mass of 469~MeV/c. The
nucleon-nucleon interaction is obtained using the HAL QCD method and its
short-distance repulsion is treated by means of ladder resummations outside the
model space. Our results show that this approach diagonalises ultraviolet
degrees of freedom correctly. Therefore, ground state energies can be obtained
from infrared extrapolations even for the relatively hard potentials of HAL
QCD. Comparing to previous Brueckner Hartree-Fock calculations, the total
binding energies are sensibly improved by the full account of many-body
correlations. The results suggest an interesting possible behaviour in which
nuclei are unbound at very large pion masses and islands of stability appear at
first around the traditional doubly-magic numbers when the pion mass is lowered
toward its physical value. The calculated one-nucleon spectral distributions
are qualitatively close to those of real nuclei even for the pseudo-scalar
meson mass considered here.Comment: 7 pages, 4 figures, RIKEN-QHP-286, RIKEN-iTHEMS-Report-1
Cancellation of Infrared Divergences in Hadronic Annihilation Decays of Heavy Quarkonia
In the framework of a newly developed factorization formalism which is based
on NRQCD, explicit cancellations are shown for the infrared divergences that
appeared in the previously calculated hadronic annihilation decay rates of
P-wave and D-wave heavy quarkonia. We extend them to a more general case that
to leading order in and next-to-leading order in , the infrared
divergences in the annihilation amplitudes of color-singlet
pair can be removed by including the contributions of
color-octet operators ,
, ... in NRQCD. We also give the decay widths of
at leading order in .Comment: 8 pages, LaTex(3 figures included), to be publishe
Rigorous QCD Predictions for Decays of P-Wave Quarkonia
Rigorous QCD predictions for decay rates of the P-wave states of heavy
quarkonia are presented. They are based on a new factorization theorem which is
valid to leading order in the heavy quark velocity and to all orders in the
running coupling constant of QCD. The decay rates for all four P states into
light hadronic or electromagnetic final states are expressed in terms of two
phenomenological parameters, whose coefficients are perturbatively calculable.
Logarithms of the binding energy encountered in previous perturbative
calculations of P-wave decays are factored into a phenomenological parameter
that is related to the probability for the heavy quark-antiquark pair to be in
a color-octet S-wave state. Applying these predictions to charmonium, we use
measured decay rates for the \chione and \chitwo to predict the decay rates
of the \chizero and .Comment: 13 page
Optical phase coherent timing of the Crab nebula pulsar with Iqueye at the ESO New Technology Telescope
The Crab nebula pulsar was observed in 2009 January and December with a novel
very fast optical photon counter, Iqueye, mounted at the ESO 3.5 m New
Technology Telescope. Thanks to the exquisite quality of the Iqueye data, we
computed accurate phase coherent timing solutions for the two observing runs
and over the entire year 2009. Our statistical uncertainty on the determination
of the phase of the main pulse and the rotational period of the pulsar for
short (a few days) time intervals are s and ~0.5 ps,
respectively. Comparison with the Jodrell Bank radio ephemerides shows that the
optical pulse leads the radio one by ~240 s in January and ~160 s in
December, in agreement with a number of other measurements performed after
1996. A third-order polynomial fit adequately describes the spin-down for the
2009 January plus December optical observations. The phase noise is consistent
with being Gaussian distributed with a dispersion of s in most observations, in agreement with theoretical expectations for
photon noise-induced phase variability.Comment: 10 pages, 5 figures. Accepted for publication in Monthly Notices of
the Royal Astronomical Societ
GUT, Neutrinos, and Baryogenesis
It is an exciting time for flavor physics. In this talk, I discuss recent
topics in baryogenesis and leptogenesis in light of new data, and implications
in B and neutrino physics. I also discuss current situation of grand unified
theories concerning coupling unification, proton decay, and indirect
consequences in lepton flavor violation and B physics. I explain attempts to
understand the origin of flavor based on flavor symmetry, in particular
"anarchy" in neutrinos.Comment: Talk presented at 5th KEK Topical Conference: Frontiers In Flavor
Physics, 20-22 Nov 2001, Tsukuba, Ibaraki, Japan. Includes comments on SUSY
GUT contribution to B->phi K
Supersymmetry, Naturalness, and Signatures at the LHC
Weak scale supersymmetry is often said to be fine-tuned, especially if the
matter content is minimal. This is not true if there is a large A term for the
top squarks. We present a systematic study on fine-tuning in minimal
supersymmetric theories and identify low energy spectra that do not lead to
severe fine-tuning. Characteristic features of these spectra are: a large A
term for the top squarks, small top squark masses, moderately large tan\beta,
and a small \mu parameter. There are classes of theories leading to these
features, which are discussed. In one class, which allows a complete
elimination of fine-tuning, the Higgsinos are the lightest among all the
superpartners of the standard model particles, leading to three nearly
degenerate neutralino/chargino states. This gives interesting signals at the
LHC -- the dilepton invariant mass distribution has a very small endpoint and
shows a particular shape determined by the Higgsino nature of the two lightest
neutralinos. We demonstrate that these signals are indeed useful in realistic
analyses by performing Monte Carlo simulations, including detector simulations
and background estimations. We also present a method that allows the
determination of all the relevant superparticle masses without using input from
particular models, despite the limited kinematical information due to short
cascades. This allows us to test various possible models, which is demonstrated
in the case of a model with mixed moduli-anomaly mediation. We also give a
simple derivation of special renormalization group properties associated with
moduli mediated supersymmetry breaking, which are relevant in a model without
fine-tuning.Comment: 56 pages, 24 figure
Toward the Ab-initio Description of Medium Mass Nuclei
As ab-initio calculations of atomic nuclei enter the A=40-100 mass range, a
great challenge is how to approach the vast majority of open-shell (degenerate)
isotopes. We add realistic three-nucleon interactions to the state of the art
many-body Green's function theory of closed-shells, and find that physics of
neutron driplines is reproduced with very good quality. Further, we introduce
the Gorkov formalism to extend ab-initio theory to semi-magic, fully
open-shell, isotopes. Proof-of-principle calculations for Ca-44 and Ni-74
confirm that this approach is indeed feasible. Combining these two advances
(open-shells and three-nucleon interactions) requires longer, technical, work
but it is otherwise within reach.Comment: Contribution to Summary Report of EURISOL Topical and Town Meetings,
15-19 October 2012; missing affiliations added and corrected errors in Tab
Evaluation of the Maudsley Addiction Profile (MAP) for use with an American Substance Abuse Population
Multi-dimensional instruments in the addiction field developed in the United States as well as in other countries are limited. The Maudsley Addiction Profile (MAP), a brief, multi-dimensional instrument developed in the United Kingdom (UK), is designed to assess the treatment outcome of individuals with alcohol and/or drug (AOD) problems and associated issues. This measure consists of sixty items across the domains of substance use, health risk, physical/ psychological health and personal/social functioning. The MAP, which has been validated on British as well as on several European samples of substance abusers, has been suggested for further validation. The current study was designed to examine the psychometric features of the MAP on a sample of American AOD users. Subjects included 133 patients who had been admitted for treatment in an inpatient psychiatric hospital; they had been identified with a recent substance abuse history. Seven interviewers were trained to criterion; 90 percent agreement with the investigator was achieved. The test-retest reliability of the MAP was good (average concordance of 0.96 across eight substances and 0.77 across health risk, health symptoms, and personal/social functioning). The interrater reliability among seven interviewers (one researcher and six clinicians) was also good (coefficients across eight substances were 0.95 and 0.78 across problem areas). The Pearson Correlation Coefficients of physical/psychological health symptoms between US and UK samples ranged between r = 0.97 and r = 0.98. Correlations among problem areas indicate several significant interactions between substance use and problem areas. Overall, the present study has shown that the MAP is a reliable outcome measure with several distinct advantages; it is an instrument which can be recommended for use in the US
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